The Role of Hydrodynamic Sorting of Seston in the Nutrition of a Benthic Suspension Feeder, Spio setosa (Polychaeta: Spionidae)

AbstractNear-bed gradients in suspended particle quality and material ingested by Spio setosa were studied using an intertidal beach population in Nova Scotia. Spio builds a sand tube that allows it to feed several centimeters above the bed, where hydrodynamic sorting of horizontal transport provides low-density, high-quality organic seston. Characterization and enumeration of particles from both worm guts and ambient sediment in the field demonstrated that guts were enriched in organic mineral aggregates relative to the bed. In a laboratory flume, worms with tubes shortened to bed level received and ingested seston of significantly lower organic quality than worms feeding in intact tubes 4–6 cm above the bed. Because tube building requires ∼2.5 days, winter beach scour which removes tubes may force Spio to feed frequently at suboptimal heights above the sediment surface. The dependence of suspension feeders on organic-mineral aggregates and the tendency for these particles to incorporate estuarine pollut...